1. Field of the Invention
The present invention relates to an air supply system for a reactor and a burner configuration for use with the reactor.
2. Discussion of the Background
Traditional hydrocarbon steam reformer reactors operate with partial or full induced combustion air supply either from natural draft or induced draft fans. Such operation makes heat recovery using air difficult, due to the very low pressure driving forces available. Reformers with pressurized combustion air supply advantageously employ combustion air for substantial heat recovery, but incur high energy penalties to compress the combustion air.
An exemplary steam reformer that utilizes compressed air is depicted in FIG. 12. The reactor 10 depicted in FIG. 12 is from U.S. Pat. No. 6,497,856 includes, within a single housing, a water gas shift section 8 at a lower end of the housing, and a steam reforming section 7 at an upper end of the housing. In such a configuration, vaporized water and fuel enter the reactor 10 at inlet 2, then enters tubes 3 wherein the flow passes through catalyst system 5 within the steam reforming section 7 and then passes through catalyst system 6 within the water gas shift section 8, and then the flow (which is now reformate) exits the reactor 10 via outlet 4.
In order to carry out the chemical processes within the reactor 10 depicted in FIG. 12, compressed air is used to cool the exterior of the tubes 3 in the water gas shift section 8, and hot combustion gas is used to heat the exterior of the tubes 3 in the steam reforming section 7. In the water gas shift section 8, cool compressed air enters the reactor 10 through a cold air inlet 12, then travels through a shell-side of the water gas shift section 8 at the lower portion of the reactor 10, and exits the reactor 10 at a hot air outlet 13. A separating wall 14 is provided to prevent air flowing within the shell-side of the water gas shift section 8 from bypassing the hot air outlet 13. After exiting through hot air outlet 13, the air travels to an external burner assembly 18 in order mix the air with fuel and ignite the mixture to produce hot combustion gas at a temperature appropriate to heat the steam reforming section 7 of the reactor 10. The hot combustion gas is injected within the reactor 10 via a heated combustion gas inlet 15. In the steam reforming section 7, the hot combustion gas enters through the inlet 15, then travels through a shell-side of the steam reforming section 7 at the upper portion of the reactor 10, and exits the reactor 10 at a cooled combustion product outlet 16. The control of the temperature of the air flowing through the shell-side of the water gas shift section 8 and the combustion gas flowing through the shell-side of the steam reforming section 7 are critical to ensure that appropriate reactions are conducted between gas flowing within tubes 3 and the catalyst systems 5 and 6 provided within the tubes.
A particular disadvantage of steam reformers using heat recovery with combustion air is the great increase in velocity, and therefore pressure drop, through a given burner with pre-heated air. Thus, for a given burner, increased heat recovery by the combustion air preheating leads to an undesirable increase in pressure loss and thus power requirement to compress the air supply.